The invention concerns a bypass valve with selective characteristics for controlled and adjustable dashpots of the type employed in motor vehicles. Such dashpots consist of a cylinder that usually accommodates an attenuating fluid. A sealed-off piston rod travels into and out of the cylinder and has a piston that separates the cylinder into compartments, one high-pressure and the other low-pressure. The piston accommodates chokes that are subject to the force of springs.
A dashpot of this type is known from German Patent 3 704 712.
An adjustable hydraulic dashpot is known from German 0S 3 711 442. It has valves in its piston. The axially moving valve body is adjusted with a wire that varies its length by way of controls.
German OS 3 631 714 discloses a hydraulic dashpot that has in addition to the other valves a bypass valve inside its piston. The bypass valve is controlled with an electromagnet. Various attenuating forces can be established by engaging the bypass in the piston along with another bypass in a bottom valve.
A hydraulic dashpot with a variable attenuation force can be derived from German OS 3 608 738. A bypass with two independently adjustable rotating slides ensures independent establishment of the attenuation force in both the pressure and the vacuum stage. The two slides create access channels with variable cross-sections inside the bypass. Also associated with each channel is a check valve. The first check valve closes during the vacuum stage and the second during the pressure stage.
German OS 3 608 841 discloses a shock absorber with a variable attenuation characteristic. A control slide with a slotted diaphragm allows the attenuating fluid through, and the motion of the slide is supposed to be unaffected by the traveling fluid.